Engine starter drive



OGL 19, 1943. 1 E BUXTCSN 2,332,054

ENGINE STARTER DRIVE Filed Dec. 9, 1941 Patented Oct. 19, 1943 *UNITE DSTATE-'S FF! CFE 2,332,054 ENGINE STARTER DRIV-E IamesE.fl'uxtomfElmira, N. Y., assigner to' Bendix Aviation Corporation, lSouthBend, Ind., a corporation of Delaware 'Application December 9, 1941,Serial No. 422,241

v,2 claims.

'che present invention relates to an engine -In those forms 'of starterdrive 'in which a 'pinion fis projected by a threaded connection intomesh with an engine geanwh'en the starting mo- `to`r is "accelerated,some form of yielding connection is necessary. The utilization of manyforms The power sha-ft 'I is provided' withl a further reduced extension6 on which a screw shaft 'I is fiiied as by means of apin 8. Screw shaft'l is provided with a smooth portion 9 and a threaded portion lll oflthe samev external tdiameter as the smooth portion 2 of the powershaft.

y 'Means for traversing and rotating the pinion 4 from the screw Vshaftis provided comprising a nut 'member SI2 normally journalled on theofrubber-like substances'to perform this function 'i0 srr'iootl'lportion 9 of 'the screw Shaft and urged yby virtue of their elasticresistance to deformainto initial engagement with the threads Il by tionhave been pro-posed, some forms tilizing the `'means of are-er'ltryspring vI3 which bears at elasticsubstance'in compressionjsomein torsion, one end against athiinble Ill anchored on the and some inboth compressionand torsion; and screw vshaft by 'a lock wire 15, LandTat 'the other each form vhas been `found to have certain adl5 endagainst `a thim'ble i6 slidably mounted on vantages and limitations forspecic uses. the screwshaft. n A flange Il on the screw shaft It is anobject of the present'invention'to prolimits the sliding movement 'ofthe thimble IG vide la novel yielding drive for engine starters `so asto denne `the idle position of the nut v.i2 `which is eiiicient andreliable in operation'and in initial engagementwith 'the end 'of 'thethreads economical in construction; H. v f

-'I-t is 'another object to provide such a device Nut -I2 is providedwith aradialange l!! havwhich `is of large torque capacity in proportioning-a splined connection as `indicated at i9 With 'to the volume oi itscushioning element. a barrel member 2i fixed to the pinion 4 at 22. Itis another object `to provide 'suena-device A Alock ring v23 is providedfor `retaining the nut in which the yielding connection comprises a i2within the barrel 2l. According tothe presrubber-like member which'isplaced-in axial shear ent invention an elastically 4deformable annular"whenthe drive is torqu'ed. y'member 2li is mounted in the barrel 2|,seated Itis a vfurther object to provide such a device on the nut I2,land so connected interiorly and -incorporating -means for vrelieving'the yielding exteriorly to the nutand barrel respectively, that memberfrom the application vof torque thereto. relative movement between thenut and barrel lIt is another object 4to provide such a device placesthe elastic member in ar'ialshear. As here yin which the engagement ofthe `pinion Withvthe shown, this is accomplished by 'bonding sleevesengine vgear is cushioned and facilitatedv bythe 2'5 .and 26 t0 theinterior and exterior of the anyielding'action of therubber-likefrn'embe'r in axial "nul'ar member 24, theinterior sleeve 25being in shear. v fabiitting relation-'with the a'nge I8 of vthe nut,liir'ther objects'and advantages will be appar- 'and thefs'l'eeve 25"being-'seated against a shoulder ent from the following descriptiontaken in cony2'! formed in the interior 'of the barrel 21. In nectionwith the accompanying drawing, in this form of the invention the member24 is which: shown as having a conical or truncated form so Fig. 1 is aside elevation partly in section of 40 arranged that when shearingstresses are apa starter drive incorporating a preferred emplied theretoduring the operation of the drive, bodiment of the present invention;the member tends to be flattened out.

Fig. 2 is a similar View of a second embodiment In the operation of thisembodiment of the inof the invention; vention, rotation of the powershaft I is trans- Fig. 3 is a detail in perspective of the yielding 45mitted through the pin 8 to the lscrew shaft 9. driving member shown inFig. 2; and The nut I2 is thereby threaded along the screw Fig. 4 is aview similar to Fig. l of a third shaft 9, moving the barrel 2| andpiniondA ahead embodiment of the invention. of it by means of theyielding member 24 until In Fig. 1 of the drawing there is illustrated athe pinion 4 meshes the engine gear 5 and enpower shaft l having asmooth reduced eXtengages the abutment shoulder 3. Thereafter furson 2providing a thrust shoulder 3 A pinion ther longitudinal movement of thenut IZ places 4 is slidably journalled on the smooth portion 2 themember24 in axial shear until the elastic of the shaft for movement into andout of enresistance to this shearing movement-l causes sufgagement witha member such as a gear 5 of cient torque to be transmitted throughsplined an engine to be started. connection I9 between the nut andbarrel to cause rotation of the pinion to crank the engine. When theengine starts, the overrunning of the engine gear returns the parts toidle position.

In the embodiment illustrated in Fig. 2, the arrangement issubstantially similar to that shown in Fig. 1 except that the annularelastic member is normally fiat, and the axial shearing forcesengendered by the transmission of torque deform the member into atruncated shape. The nut l2 is provided with an abutment shoulder I0 forspacing the sleeve 25 from the ange I8 in order to permit thistelescoping movement of the parts. In this form also, the step 2 of thepower shaft I is removed in order to permit the use of a smaller drivepinion 4. y

The operation of this embodiment of the invention is substantially thesame as above set forth.

In Fig. 4 there is illustrated a power shaft 3l having a smooth reducedportion 32 providing a stop shoulder 33 and a splined portion 34. Ascrew shaft 35 is slidably keyed on the splined portion 34 of the powershaft, normally abutting against a ring 36 pressed on the splinedportion 34 of the shaft until stopped by the run-out 3l of the splines.

Screw shaft 35 is provided with a threaded portion 38 and a smoothportion 39 on which is normally mounted a nut member 4I having a radialflange 42. A pinion 43 is slidably journalled on the smooth portion 32of the power shaft for movement into engagement with an engine gear 44.A barrel member 45 is iixed at 46 to the pinion and is keyed to theflange 42 of the nut as indicated at 4l, the fiange being retained inthe barrel by means of a lock ring 48. A re-entry spring -49 is providedbetween the rin-g 36 and the end of the barrel 45 for urging the nut 4Iinto initial engagement with the threads 3B, and an anti-drift spring 5llocated between the ring 36 and the flange 42 of the nut normallymaintains the nut and its associated parts in idle position.

According to the present invention longitudinal movement of the screwshaft 35 away from the engine gear is resisted by an elasticallydeformable member which is thereby placed in pure axial shear. As hereshown this is accomplished by means of an outer barrel member 52 seatedon the end of the power shaft 3| in abutting relation with the ends 53of the splines 34 and clamped there-against by a nut 54 threaded on theend of the power shaft. An elastically deformable ring 55 has sleeves 56and 51 bonded to its interior and exterior surfaces respectively, andthese sleeves are arranged to seat on the end of the screw shaft 35 andthe interior of the barrel 52 against a shoulder 58 on the screw shaftand a shoulder 5S in the barrel respectively.

In the operation of this embodiment of the invention rotation of thepower shaft 3l is transmitted to the screw shaft 35 through the splines34, thereby causing the nut 4l to be threaded along the screw shaftuntil the pinion 43 is moved into mesh with the engine gear 44 andagainst the stop shoulder 33. Further rotation of the screw shaft causesit to be moved away from the engine gear, thus applying a shearing forceto the ring 55 until the resistance of the ring is built up sufficientlyso that the resultant torque transmitted from the nut 4| through thebarrel 45 to the pinion causes the pinion to rotate and crank theengine.

It will be appreciated that in all the embodiments of the inventionillustrated, the capacity of the yielding connection for thetransmission of force is large in comparison with the size of thatmember inasmuch as all parts of the member are placed simultaneouslyunder stress, and the supercial areas transmitting such stress arelarge. The fact that in each case, the torque is transmitted through apositive mechanical connection under the control of the yielding shearmember, also renders the torque capacity of the device large incomparison to the volume of the yielding member.

Although certain embodiments of the invention have been shown anddescribed in detail, it will be understood that other embodiments arepossible, and that changes may be made in the design and arrangement ofthe parts without departing from the spirit of the invention as definedin the claims appended hereto.

What is claimed is:

l. In an engine starter drive a pair of concentric spaced Cylinders, acylinder of elastica-ily deformable material interiorly and exteriorlyconnected to said members respectively, torqueresponsive means forimparting relative axial movement to said members, and means preventingrelative rotation between said members.

2. In an engine starter drive a power shaft, a pinion slidablyjournalled thereon for engagement with an engine member, means includinginter-threaded members for traversing and rotating the pinion, saidmeans including concentric cylindrical members positively connected forrotation in unison with freedom for relative longitudinal movement, anda ring of elastically deformable material having bonded connectionsinteriorly and exteriorly to said concentric members respectively.

JAMES E. BUXTON.

